Skin is the largest organ of the human body with several important functions, including forming a physical barrier to the environment, protection against microorganisms, allowing and limiting the inward and outward passage of water and electrolytes, ultraviolent radiation and toxic agents. Within the skin there are three structural layers: the epidermis, the dermis and the subcutis. Keratinocytes are the main cell type found within the epidermis. Fibroblasts are the predominant cell type within the dermis. The dermis is composed of a supportive extracellular matrix and contains bundles of collagen which run parallel to the skin surface. The role of fibroblasts within the dermis is to produce collagen, elastin, and structural proteoglycans. The collagen fibers constitute 70% of the dermis, giving it strength and toughness while elastin provides normal elasticity and flexibility. The proteoglycans provide viscosity and hydration. Transforming growth factor β (TGF-β) is associated with the regulation of extracellular matrix production in human skin connective tissue. This factor is also of importance in the process of wound healing. Skin also is innervated and vascularized, and also contains small numbers of immune cells (e.g. mast cells, tissue macrophages, etc.).
Aging of human skin is associated with discoloration, wrinkling, and the sagging effect. These developments related to aging are dramatically visible in human skin which becomes dry, wrinkled, lax, and irregularly pigmented over time. Typically, aged skin is characterized by a flattening of the dermal-epidermal junction, increased atrophy, and a loss of elasticity of the dermal connective tissue. The loss of firmness and elasticity is commonly associated with the decrease/loss and disorganization of the major extracellular components, including collagen I (associated with being the primary cause of wrinkle formation), elastin, and large and small proteoglycans and glycosaminoglycans. Aging skin also possesses decreased TGF-β which results in reduced production of collagen and compromised wound healing. A histological analysis of aging in human skin has revealed a decrease in tissue thickness, disorganization of collagen, and accumulation of non-functional elastin.
Handheld skin cleansing devices are used for cosmetic purposes to efficiently cleanse facial skin. In some cases the devices claim additional benefits, such as exfoliation, smoothing/resurfacing, or deep cleaning. Such devices have one or more discrete electrically powered bristle brushes or nonwoven fabric pads that oscillate, vibrate, or a combination thereof to provide mechanical action of the brush(es) or pad(s) against the skin. Typically, a cleanser is applied to the bristles or the pad. Cleansing effectiveness of these devices depends on the bristle or pad type, pressure applied, and the type of cleanser.
One example of many is the SonicDermabrasion Facial Brush ST255, sold by PRETIKA® Corp. of Laguna Hills, Calif. The brush includes a handle and a round bristle brush head that rotates. Another example is the Pore Sonic Cleanser sold by Pobling of Seoul, South Korea, which includes an oblong brush that is vibrated. A further example is found in U.S. Patent Application Publication 2012/0233798 for BRUSHHEAD FOR ELECTRIC SKIN BRUSH APPLIANCE, published Sep. 20, 2012. Another example is the MIA 1®, MIA 2®, and MIA 3®, sold by CLARISONIC® of Redmond, Wash. A further example is the PRO X® Facial Brush by Procter & Gamble of Cincinnati, Ohio. Many examples similar to these are easily found in department stores, drug stores, and online.
Such rotating and/or vibrating heads provide cleaning action that is superior to the use of hands to clean one's face. However, the brushes and pads only reach the surface of the topmost layer of skin cells. Brush tips do not effectively reach the interstitial spaces between cells or other fine skin features where dirt or dead cells may be trapped, and thus do not effectively clean such spaces. Additionally, brushes tend to build up a combination of cleansers, dirt, bacteria, and dead skin cells at the base of the bristles that is difficult or impossible to clean off. Finally, brushes used for facial cleansing tend to lift, but not remove facial skin cells. Thus, brushes can actually have a skin roughening effect.